Synergistic chemical control of nutsedge with combination of a 1-methyl-4-phenyl-pyridinium salt and a cyclopropylamino-triazine herbicide

ABSTRACT

Nutsedge is combated with quaternary 4-phenyl-pyridinium salts, for example 1-methyl-4-phenylpyridinium chloride, in synergistic combination with at least one interacting herbicide selected from the group consisting of 2,4-DB, 2-chloro-4-cyclopropylamino-6isopropylamino-s-triazine and dicamba.

United States Patent [191 Ahle [451 May 20, 1975 1 SYNERGISTIC CHEMICAL CONTROL OF NUTSEDGE WITH COMBINATION OF A l-METHYL-4-PHENYL-PYRIDINIUM SALT AND A CYCLOPROPYLAMINO-TRIAZINE HERBICIDE [75] Inventor: James L. Ahle, Shawnee, Kans.

[73] Assignee: Gulf Research & Development Company, Pittsburgh, Pa.

22 Filed: on. 30, 1973 211 App]. No.: 411,126

Related US. Application Data [62] Division of Ser. No. 288,645, Sept. 13, 1972,

abandoned.

[52] US. Cl. 71/93; 71/94; 71/115; 71/116 [51] Int. Cl. A0ln [58] Field of Search 71/93, 94

[56] References Cited UNITED STATES PATENTS 3,503,971 3/1970 Neighbors et a1 71/93 3,713,807 l/1973 Schwartzbeck 71/93 3,737,299 6/1973 Hedrich 71/94 Primary Examiner-Glennon l-I. Hollrah [57] ABSTRACT Nutsedge is combated with quaternary 4-phenylpyridinium salts, for example 1-methyl-4- phenylpyridinium chloride, in synergistic combination with at least one interacting herbicide selected from the group consisting of 2,4-DB, 2-chloro-4- cyclopropy1amino-6-isopropy1amino-s-triazine and dicamba.

2 Claims, No Drawings SYNERGISTIC CHEMICAL CONTROL OF NUTSEDGE WITH COMBINATION OF A l-METHYL-4-PHENYL-PYRIDINIUM SALT AND A CYCLOPROPYLAMINO-TRIAZINE HERBICIDE This is a division of application Ser. No. 288,645, filed Sept. 13, 1972, now abandoned.

DESCRIPTION OF THE INVENTION Nutsedge is a perennial weed which reproduces by underground tubers or nuts as well as by seeding, the common species of which resist most herbicides and represent the most troublesome weeds in world agriculture. In the case of purple nutsedge, rhizomes emerge from the tubers and grow underground. At the end of a rhizome a basal bulb forms just below the soil surface and gives rise to another plant. More rhizomes grow from the basal bulb. More basal bulbs form at the end of these rhizomes and the cycle repeats. Tuber chains start forming after weeks and long chains are present after 18 weeks. After 20 weeks, a field that began with one tuber per square foot may have 83,000 plants, 114,000 bulbs and 260,000 tubers in a single acre.

Many of the tubers are dormant and do not germinate unless the tuber chain is broken by plowingor cultivating. Mechanical methods of control of nutsedge tend to increase the rate of multiplication of plants. The underground tubers appear to remain viable in spite of the use of herbicides and there are always a few wind-borne seeds in the field to assure the reestablishment of nutsedge infestation. Even with the best chemical weed control of nutsedge the application of herbicides must be repeated during each growing season because of the remarkable ability of this weed to re-establish itself. Weed control agents with selective toxicity to nutsedge, but which are safe on a wide variety of crops are obviously very desirable. It has recently been discovered that quaternary 4-phenylpyridinium halides are effective chemical agents for combating nutsedge. I have discovered that the effectiveness of these compounds is beneficiated by synergistic interaction with 2,4-DB, 2-chloro-4-cyclopropylamine-6-isopropylamino-s-triazine and dicamba, so that by use of the synergistic combinations of these agents, nutsedge can be controlled with virtually no permanent injury to a number of crops, including soybeans, peanuts, rice, oats, wheat, grain sorghum and corn in some instances. Briefly, the method of this invention consists of applying to the locus of the nutsedge plants an effective amount of a combination of 1 part by weight of a quaternary 4-phenylpyridinium salt with from 1/10 to 1 part by weight of an interacting herbicide selected from 2,4-DB, 2-ch1oro-4-cyclopropylamino-6-isopropylamino-s-traizine and dicamba, sufficient to produce a synergistic herbicidal effect on nutsedge. The

, following discussion is presented in an effort to review present knowledge of the nature of synergism and explain the manner in which evidence of synergism is presented herein.

I-IERBICIDE INTERACTION In the use of herbicides or other pesticides it is seldom that one specific pesticide does everything that the user desires to accomplish. In an effort to obtain the best of all possible characteristics possesed by two or more pesticides it has become common practice to use these substances in various combinations. The results obtained by the use of combinations of herbicides are usually about what would be expected if one considers carefully the nature of the selectivity patterns of the individual chemicals in a combination. Selectivity is normally a relative, not an absolute characteristic. A chemical is often safe to use on a particular crop because the minimum effective dose for crop injury barely exceeds the minimum dose for complete control of the weeds. Unfortunately the borderline toxicities in the selectivity patterns of individual herbicides often add together when herbicides are combined, so that the combination is no longer safe on as many crop species as any one of the herbicides taken alone. Herbicide combinations are therefore usually recommended for use in only one or two crops. This type of result might be classified as a neutral one, indicating no particular effect of any herbicide on another.

Occasionally there is evidence of antagonism by the specific herbicides in a combination, which manifests itself in an unexpected failure to control some specific weed. More rarely, a combination of herbicides possesses such effectiveness against some undesirable plant species that the result cannot be explained on the basis of known phytotoxicity of the individual components of the combinations. These unexpected increases in effectiveness of chemical agents have been observed, for example, in herbicides, insecticides and chemotherapeutic agents. Probably because these effects defy all attempts at explanation, the term synergism has been employed to describe the phenomenon. Presumably this term was selected because it originally was used to identify the ancient theological doctrine or belief that there is a cooperation of divine grace with human activity. Thus, since we can find no other reason for the unexpected beneficial results, they are attributed to the influence of divine assistance. 1

Although there is no precise definition of synergism, a synergist is defined clearly as an agent that increases the effectiveness of another agent when combined with it. This definition includes both active pesticides and substances which have no effectiveness at all, if they interact with pesticides to improve effectiveness.

In the case of combinations of herbicides, the term synergism is now used generally to indicate a response in excess of that expected from the sum of the effects of various chemicals when used separately under the same conditions. There are various ways of interpreting data so as to identify and estimate the extent of synergism.

In order to determine whether or not an unexpected interaction of two or more herbicides has occurred it is necessary first of all to decide just what constitutes expected behavior. The determination of the expected effect if difficult and can only occasionally be established by simple summation of numerical scores of the responses obtained with each chemical used separately. In a combination of herbicides, when one chemical has already killed a number of individual plants, the other chemical may appear to be either more or less effective than when used individually, depending upon'various factors, including the level of effectiveness which is arbitrarilyselected for comparison purposes and on the degree to which susceptibility to the two toxicants is related. If the two toxicants affect the plant by different biochemical mechanisms, the evidence of synergism may be dramatically apparent. However, if both toxicants operate by the same mechanism, the evidence of synergism may be erratic, only becoming clearly apparent when both toxicants are employed at application rates substantially above the level of minimum observable effect (threshhold). The occurrence of different threshhold application rates below which toxicants are ineffective, or in other words, the variation of regression of response to dose of individual herbicides, makes it extremely difficult to determine precisely what herbicidal response would be reasonably expected from a herbicide combination. This problem has been given considerable attention by research workers in this field and various methods of obtaining and treating data have been proposed.

Graphical methods of treating data include the plotting of percentage of plant growth response (measured by weight of new growth) versus herbicide application rate, percentage response versus logarithm of herbicide application rate and the reciprocals of percentage response versus reciprocals of herbicide application rate. Herbicide antagonism or synergism is indicated by differences in slope of straight line plots and in differences in shape of curves. (Growing, D. P. 1960. Comments on Tests of Herbicide Mixtures. Weeds 8: 379-391.)

Efforts have been made to place numerical values on synergistic and antagonistic effects in herbicide combinations. For example, the expected response for a combination of herbicides may be determined by taking the product of the percent-of-control values for individual herbicides applied alone and dividing by (100)" where n is the number of herbicides in the combination. (Colby, S. R. 1967. Calculating synergistic and antagonistic responses of herbicide combinations. Weeds 15: 20-22.)

Another approach to evaluation of interaction of herbicides has been to average the herbicide control scores on a number of plant species, both for combinations and for the individual herbicides. An increase in the average rating of a combination over the average ratings for the same total amount of either pesticide applied alone has been considered to indicate a synergistic effect. A strange thing about the use of the averaging approach is that an increase in average control may be observed while at the same time no additional species is controlled effectively. The increase in average ratings may occur entirely as a result of a general increase in apparent toxicity, resulting from the additive overlapping of borderline toxicity in the selectivity patterns, as discussed above. (See, for example, US. Pat. No. 3,535,102.)

In other efforts to put a quantitative value on cotoxicity results, the concept of the cotoxicity coefficient has been employed. (The method of Yen-Pei Sun and E. R. Johnson, Journal of Economic Entomology, vol. 53, 887-892.) In general, all mathematical methods of treating data on herbicide interaction suffer from the low level of mathematical significance in the data.

Another concept which has been employed is a graphic one in which the rate of application of one pesticide in a combination versus the rate of application of another pesticide in the combination is plotted for one specific level of effectiveness, for example, 50% control or inhibition of growth on one plant species. If there is no interaction'of the two pesticides the graph should theoretically be a straight line. These graphs, called isoboles, sometimes show both synergism and antagonism withincertain ranges of composition and may indicate both interaction and non-interaction of the two pesticides at various ratios of components in the pesticide combination. (Colby, S. R. and R. W. Feeney, 19 67. Herbicidal Interactions of Potassium Azide with Calcium'Cyanamid. Weeds (2): 163-167, 7

tion in the field. As concentration on the plants declines during the days after application, the synergistic effect will sustain the effectiveness of the herbicide combination for a longer period of time than normally expected, resulting in the killing of many severely injured weeds which might otherwise recover and produce seed in the field. The plotting of isoboles for combinations of two herbicides at the level of severe injury, at which only a few of the test plants fail to die, therefore reveals herbicide interactions of special significance with respect to utility.

The use of the herbicides both individually and in synergistic combination so as to obtain reliable measures of herbicidal effects may be performed according to the procedures discussed below.

USE OF THE HERBICIDES There are described below illustrative procedures for use of the herbicidal compounds under controlled conditions in the greenhouse, so as to obtain data on phytotoxic activity and selectivity.

l. Post-Emergent Use (Initial Tests) An aqueous dispersion of each active compound is prepared by combining 0.4 gram of the compound with about 4 ml of a solvent-emulsifier mixture (3 parts of a commercial polyoxyethylated vegetable oil ernmul-.

sifier, one part xylene, one part kerosene) and then adding water, with stirring, to a final volume of 40 ml. The species of plants on which each compound is to be tested are planted in 4-inch pots in a greenhouse. 10 to 14 days after emergence of the plants, one pot of each species is sprayed with an aqueous dispersion of the active compound prepared as described above, at a rate of 5 lb of active compound per acre and at a spray volume of 60 gallons per acre. Approximately 12 days after the spray application the plants are observed and the results rated.

Pre-emergent herbicidal test results may be obtained according to the procedure described below.

2. Pre-Emergent Use (Initial Tests) A solution of each active compound is prepared by dissolving 104 mg of the compound to be tested in 100 ml of acetone. Disposable expanded polystyrene trays about 2 /2 inches deep and about 1 square foot in area are prepared, seeded, and sprayed with the acetone solution at the rate of 10 lb of active chemical per acre of sprayed area and are then covered with about onefourth inch of soil. One group of trays, which have been seeded with alfalfa, brome, flax, oats, radishes and sugar beets is held at F day temperature; another set of trays seeded with corn, coxcomb, cotton, crabgrass, millet and soybeans is held at F. Twenty-one days after seeding and treatment the plantings are examined and herbicidal effects are rated according to the schedule as described in the following discussion.

THE RATING OF HERBICIDE TEST RESULTS So as to assure that the numerical data from greenhouse tests are significant, the scores of the observations recorded herein are limited to only five specific ratings which are judgments made as discussed below:

0 (No Effect) This rating, as with all the other ratings, is determined by comparison with test plants grown under identical conditions but without treatment with herbicides. If no difference between the untreated plants and herbicide-treated plants is observable, the rating is O.

l (Slight Effect) If there is stunting, slight difference in color, a few dead leaves or other effect which is definitely different from the check plants but from which the plants appear to have recovered, the rating is I. It is true that the plants may prove to be a bit retarded and may flower or mature a little later than the check plants if retained in the greenhouse, but experience has shown that plants given this rating are otherwise normal. The rating indicates only a difference in appearance which shows that a temporary effect has occurred.

2 (Moderate Effect) Plants which exhibit substantial permanent injury of various sorts, but in which all individuals are still alive are given a rating of 2. Only a few species merit holding in the greenhouse for another 2 or 3 weeks to determine whether this rating is accurate. Experience has taught the applicant that no matter how sick it looks, a nutsedge plant of substantial size usually recovers and a tentative rating of 2 may have to be finally called 1. Occasionally on some plant species the condition of new growth shows increasing indication of injury during the last 2 or 3 days of the test. These plants may be held for further observation to see if the rating must be changed to 3.

3 (Severe .Effect) When injury is readily apparent and most, but not all plants are dead in every pot, the rating is 3. Occasionally these pots are held for a further length of time to determine if the other plants are dying. If all of them are, the rating is changedto 4.

4 (Complete Control) When all the plants in one set of pots die, the rating is 4. This rating is reliable and usually repeatable, but is less significant than a rating of 3 from the scientific standpoint. There are no distinctions between dead plants; therefore some may have received only suffi-.

SOURCES OF VARIATIONS IN GREENHOUSE TEST RESULTS Quantitative results obtained from working with living plants are always subject to some variations, the principal sources of which are discussed below. j

1. Duration and Intensity of Sunlight A definite variation in test results is observed when experiments conducted in cloudy weather are compared with those performed in periods of intense sunlight. In general, cloudy weather appears to have the effect of weakening of the plants so that herbicide ratings are a little higher. There are also some unexplained variations in test results with the season of the year which may be attributable to differences in intensity, duration and angle of incidence of sunlight.

2. The Nature of Individual Seeds This is a troublesome, uncontrollable experimental variable. Weed seeds are not as uniform as crop seeds, regardless of the source of supply. Weeds are notoriously variable in genetic make-up, having such a great variety of heredity among individual plants that within only a few generations of survivors they easily establish weed populations which resist adverse conditions of climate, soils, shading, herbicides and so forth.

3. Temperature In mid-summer, excessively high temperatures may occur in greenhouses in the temperate climate zones in spite of best efforts to keep the temperature under control. Tests are customarily suspended during extremely hot weather, during which time greenhouses may be shut down for cleaning and maintenance. During the rest of the year, temperatures may be kept substantially constant during testing and this is therefore not a serious source of error.

4. Changing Length of Days Although the overall intensity and distribution of wavelengths of natural sunlight cannot, in the present state of the art, be duplicated exactly by artificial light, the length of days may be regulated to a constant value by means of artificial lights of a modern type which are manufactured and sold for this purpose. The triggering of flowering, dormancy and other behavior of plants in response to changing length of days is'in this way substantially eliminated as source of error.

5. Variation in Stage of Growth of Test Plants As plants grow and develop, there are significant differences in sensitivity to herbicides at different stages of growth. When tests are made at different times, with different plants, results are not strictly comparable unless the test plants are sprayed at precisely the same stage of growth. In general, larger, more mature plants are more resistant to post-emergent herbicides than are younger plants. Since stage of growth of weeds is only one of many uncontrolled variables in the use of herbicides outdoors in fields of growing crops, the results obtained in the field are generally less reproducible than results of greenhouse tests.

SELECTION OF PLANT SPECIES FOR GREENHOUSE TESTING COMMON NAME SCIENTIFIC NAME Crabgrass Digilaria sanguinalis Bromus inermis Brome COMMON NAME Sugar beet Cockscomb Gennan millet Radish -Continued SCIENTIFIC NAME Bola rulgaris Celusia plumuxa Samria italica Rapllanux salivux The following dissimilar plant species may also be 10 employed in initial post-emergent herbicide tests:

COMMON NAME SCIENTIFIC NAME In further greenhouse tests to define the selectivity patterns and indicate extent of utility of herbicides, the following dissimilar species may be conveniently em- COMMON NAME Continued SCIENTIFIC NAME Rape Turnip Strawberry Bush bean Lima bean White clover Peas Red clover Flax Carrot Sweet peppers Potato I Tobacco C antaloupe Cucumber Squash Watermelon Lettuce Safflower Brussica napus Brassica rapa F ragaria sp. Phaseolus vulgaris Phaseolus Iimensis Trij'olium repens Pisum .rativum Trifulium pralenxe Linum usilalissimum Caucus carota Capsicum grassum Solamum tuberosum Nic'otiana mbatum Cucumis melo C ucumis salivus Cucurbita maxima Cilrullus vulgaris Lacluca saliva Carlhanus tinctorias To further evaluate the utility of a herbicide in weed control, tests may be made on species of weeds selected from the following list:

ployed:

COMMON NAME SCIENTIFIC NAME I Fall panicum Panicum dichotomiflorum COMMON NAME SCIENTIFIC NAME Yellow foxtail Setaria glauca Cheat Bromus secalinus Plgweed Amaranlhus retroflexux Raoul grass Roltbaellia exultala Lambsquarters Chenopadium album Quackgrass Agropyron repens Wild buckwheat Palygrmum convolvulus Johnson grass Sorghum halepense Wild mustard Brassica kaher Sesbania Sesbania exallata Cocklebur Xanthium pensylvanicum sBicklepod d Cassia obtuslfolia Morning glory lponwea purpurea egga ee Dexmodium tartuosum Crabgrass Digiraria .ranguinalis Velvetleaf Abuti lon theophrasli Downy bronl1e gromus IeLctOrum lsgc l gochzla scoplarm Giant oxtai elaria a erii I'S ane orlu aca 0 eracea Barnyard grass Echinoc hloa crusgalli 3 5 Black g tsh sala um nigrum Green foxtail Setaria viridis llmsvnweed Dalian slramtmium wild cane S h b l Sunflower Heliantlau annuus Wild oats Avena falua Ragweed Ambr P- Iclenow nutsedge gyperm: 2 7 l l flii pusley i'gz r siyiimbm 323 fjgig ig g i Smartweed Polyganum pennsylvahicum Tomato Lycospersicum esculemum 40 ggg g g g' g fjgg g gz g g beets g vulgar White cockle Lychn is alba fi -gig Jig-ZZZ Saliva Dandelion Taraxaoum officiizale Com Zea mays Buckhom plantain Planlaga lanceolata Grain sorghum Sorghum vulgare Wheat Trilicum aestivum Rice Oryza sativa AQUATIC WEEDS So as to further evaluate characteristics of herbicides with respect to crop injury, tests may be made on various crop species, for example, species selected from the following list:

COMMON NAME Sugar cane Sweet corn Pop corn Perennial ryegrass Kentucky bluegrass Kentucky 3| fescue Wheat Barley Rye Sudan grass Atlas sorgo Creeping red fescue Onion Buckwheat Table beets Spinach Cabbage SCIENTIFIC NAME Saccharum officinarum Zea mays Zea mays Lolium perenne Poa pralense Festuca elatior Triticum aeslivum Hordeum vulgare Secale cereale Sorghum vulgare Sorghum vulgare Fesluca rubra Allium cepa Fagopyrum sagiualum Bela vulgaris Spinocia deracea Brassica olcracea Cabomba Salvinia Duckweed Azolla Elodea Watermilfoil Cabomba caroliniana Salvinia rolundifolia Lemma minor Azolla caroliniana Hydrilla verticillata Myriophyllum specatum TABLE I POST-EMERGENT EFFECTS PLANT SPECIES Barnv Rate Crabyard Soy- Morning Nut Wild Shatter Grain COM- Lb/A grass grass bean glory Peanut sedge Rice oats' Wheat cane sorghum Corn POUND 1 1 l-Methyl- 4 1 i 1 1 1 -0 4 1 1 2 2 2 1 4-phenyl- 2 1 1 l l 1 0- 3.4 1 0 1 1 1 l pyridinium 1% 4 chloride 1 /4 4 1 0 0 1 0 0 2.3 Q 0 0 0 0- 0 Va 0 0 0 0 0 2.2 0 O 0 0 0 0 2 Dicamba 4 4 3 3 2 2 3 3 3 4 2,2 3 3 3 3 2 2 A 0 1 4 4 3 0 1 l l 1 1 1 A: 0 0 4 4 2 0 O l 1 0 0 0 2,4-DB 4 3 3 2 2 0 0 2 4 l 0,2 1 l 1 1 1 0 A 0 0 l 4 O 0 0 0 0 0 0 O A; O 0 l 4 0 0 0 0 0 0 0 O 2-Chloro 3 4 4-cyclo- 2 4 4 4 4 4 3,3 4 4 4 4 4 1 propylk 4 4 4 4 2 O 4 4 '4 3 2 0 amino-6- A 3 4 4 4 2 0 4 4 4 1 1 0 isopropylamino-striazine Application of Synergists in Combination with 1 lb per acre of l-Methyl-4-Phenylpyririnium chloride SYNERGIST Dicamba A 0 l 4 4 3 4 2 2 2 l 1 1 A; 0 0 4 4 3 4,4 1 l l l (l 0 2,4-DB A 1 O 1 4 0 4,4 0 O 0 1 1 0 Va 1 O 1 4 0 3,4 0 0 0 l l 0 1/16 4 PLANT SPECIES Bam- Rate Crabyard Soy- Morning Nut- Wild Shatter Grain SYNERGlST Lh/A grass grass bean glory Peanut sedge Rice oats Wheat cane sorghum Com Z-Chloro- A 4 4 4 4 3 4 4 4 4 3 2 0 4-cyclo- 4 4 .4 4 4 4 3 4 4 4 4 3 2 0 P py amino-6- isopropyl amino-striazine APPLlCATlON OF SYNERGISTS ON NUTSEDGE lN COMBINATION WITH 1% LB AND A LB PER ACRE OF l-METHYL-4-PHENYLPYRlDlNlUM CHLORIDE RATlNG ON NUTSEDGE Appln Rate with V: lb of with 1 lb of SYNERGlST lb/A quaternary salt quaternary salt Dicamba Va 3 4 1/16 2 3 2,4-DB A 3 4 /a 2 4 1/16 2 3 2-Chloro-4-cyclo- 3 4 propylamino-6- Va 3 3 isopropylaminos-triazine Where more than one score is recorded on nutsedge in the above tests it indicates the average results obtained in different sets of experiments conducted at different times of the year.

It will be seen from these data that the herbicide combinations of this invention are effective on nutsedge and a few other pests, particularly morning glory, but appear to be safe on grain crops and in the case of the combination of 2,4-DB are also safe on peanuts and soybeans. In the drawing there are plotted isoboles at the level of severe injury'(rating of 3) on nutsedge, of the combinations of herbicides employed in the I claim:

1. The method of combating nutsed'ge consisting of applying post-emergently to the locus of nutsedge plants an effective amount, at least five-eighths lb per acre of a synergistic combination of l-methyl-4- phenylpyridinium chloride with from 0.1 to 1.0 parts by weight of 2-Chloro-4-cyclopropylamino--isopropylamino-s-triazine and an inert carrier.

2. The synergistic nutsedge toxicant composition consisting essentially of an effective amount of a combination of one part by weight 2-chloro-4- cyclopropylamino-6-isopropylamino-s-triazine with from 2 to 6 parts by weight l-methyl-4- phenylpyridinium chloride and an inert carrier. 

1. THE METHOD OF COMBATING NUTSEDGE CONSISTING OF APPLYING POST-EMERGENTLY TO THE LOCUS OF NUTSEDGE PLANTS AN EFFECTIVE AMOUNT AT LEAST FIVE-EIGHTS LB PER ACRE OF A SYNERGISTIC COMBINATION OF 1-METHYL-1-4-PHENYLPYRIDINIUM CHLORIDE WITH FROM 0.1 TO 1:0 PARTS BY WEIGHT OF 2-CHLORO-4-CYCLOPROPYLAMINO-6ISOPROPYLAMINO-S-TRIAZINE AND AN INERT CARRIER.
 2. The synergistic nutsedge toxicant composition consisting essentially of an effective amount of a combination of one part by weight 2-chloro-4-cyclopropylamino-6-isopropylamino-s-triazine with from 2 tO 6 parts by weight 1-methyl-4-phenylpyridinium chloride and an inert carrier. 